Abstract
Feline eyelid hidrocystoma is a rarely reported disease of the apocrine glands of Moll that has been variably interpreted as proliferative/neoplastic lesion or retention cyst. The purpose of this paper was to investigate feline hidrocystoma pathogenesis by means of a histological and immunohistochemical study. Nine paraffin embedded biopsies of eyelid hidrocystoma were retrieved from our archives. Histological sections were immunostained with antibodies anti-cytoskeletal proteins and Ki67 antigen. All hidrocystomas were observed in Persian cats, seven males/two females, mean age 9.6 years. Histologically, single or multiple, variably sized cysts expanded eyelid dermis. Cyst was lined by cuboidal epithelium, occasionally raising in papillary structures. Immunostaining was consistent with apocrine gland epithelium (cytokeratin 8/18; 19 and 14 positive). Ki67 immunolabelled nuclei ranged from 5.3 to 20.83%. Although it was not possible to draw a definite conclusion concerning hidrocystoma aetiopathogenesis, the relatively high Ki67-proliferative index observed, suggested a proliferative nature of the lesion.
Moll's glands are modified sweat glands located at the margin of the eyelids and in the overlying epidermis of the lid. 1,2 The structure and location of the glands of Moll are similar in all domestic species. 1 The histological features of Moll's glands are consistent with apocrine glands, however, their function is still unknown both in humans and in animals. 1,2 The presence of a variety of antimicrobial proteins (eg, lysozyme, β-defensin-2, adrenomedullin, lactoferrin, and IgA) in Moll's gland secretions in primates has suggested their contribution in ocular host defence. 2 Similar studies have not been performed in domestic species.
Single or multiple benign cystic lesions of the eyelid, originating from the glands of Moll are referred, in man, as apocrine hidrocystoma. 3,4 The aetiopathogenesis of apocrine hidrocystoma is currently unknown and the lesion has been variably interpreted either as proliferative adenomatous tumour 5–7 or as retention cyst caused by excretory duct obstruction. 8
The veterinary literature reports only a few cases of multiple eyelid cystic lesions/hidrocystomas in cats. 9–12 Most eyelid hidrocystomas have been reported in Persian cats, suggesting a possible breed predisposition. 10 In most of reported cases, when follow-up data were available, additional cysts developed 11 months to 5 years after surgical removal.
The aim of our study was to contribute to a better understanding of the pathogenesis and the histological characterisation of eyelid apocrine hidrocystoma. To the authors' best knowledge this study presents the largest collection of feline eyelid hidrocystomas reported so far.
Materials and Methods
Paraffin embedded excisional biopsies of feline eyelids with a histopathological diagnosis of apocrine cystic lesion were retrieved from the archive of the Division of Veterinary Pathology (2003–2007). Clinical records and histological slides were reviewed. Nine cases of lesions consistent with a histological diagnosis of hidrocystoma were selected.
Data concerning clinical presentation and follow-up were obtained, for these nine cases, by contacting referring ophthalmologists.
Five microns serial sections were obtained from paraffin blocks, and stained with haematoxylin and eosin (HE) and Mallory. Additional serial sections were obtained from 8/9 specimens and immunoassayed with the standard ABC method, 13 with antibodies anti-α smooth muscle actin (SMA) (clone 1A4), cytokeratin 14 (clone LL002), cytokeratin 8/18 (clone UCD/PR-10.11), cytokeratin 19 (clone b170) and Ki67 (clone MIB1). Aminoethylcarbazole (AEC) was used as a chromogen. In one case embedded material was insufficient for further sections. Antibody origin, dilution and antigen retrieval methods are summarised in Table 1.
Table 1.
Antibodies used, clone dilution and unmasking technique adopted
| Antibody | Clone | Host | Source | Dilution | Retrival method |
|---|---|---|---|---|---|
| α SMA | 1A4 | Mouse | Dako Cytomation Denmark A/S | 1:2000 | None |
| Ki-67 | MIB1 | Mouse | Dako Cytomation Denmark A/S | 1:600 | Pressure steamer, buffer citrate (pH 6), 20 min |
| CK 8/18 | UCD/PR-10.11 | Mouse | Zymed Lab, CA, US | 1:200 | Pepsin digestion (37°C) 10 min |
| CK 14 | LL002 | Mouse | Neomarkers, CA, US | 1:2000 | Pressure steamer, buffer citrate (pH 6), 10 min |
| CK 19 | b170 | Mouse | Novocastra Lab, UK | 1:200 | Pepsin digestion (37°C) 10 min |
The extent of fibrosis in the dermis surrounding cystic lesions was semi-quantitatively evaluated on Mallory stained sections and scored as absent (0), mild (+) moderate (++) and severe (+++).
Expression of Ki67 (MIB1) was quantitatively assessed with a video camera (CoolSNAP-Pro cf, Media Cybernetics) linked to an automatic image analysis system (Image Pro Plus 4.5, Media Cybernetics). In 10 random high power fields (HPF, 400×), the number of MIB1 positive stained nuclei and the total number of cell nuclei were evaluated and the relative percentage of stained nuclei was calculated and indicated as proliferative index (PI).
Results
Nine hidrocystomas were obtained from a total of 1658 feline biopsies (of which 54 were eyelid lesions). All hidrocystomas were diagnosed in Persian cats, seven males, two females, aged, at the time of diagnosis, 3–15 years old (mean 9.6; median 8.5). Clinical data and the main pathological results are summarised in Table 2.
Table 2.
Clinical data and the main pathological results
| Case | Sex | Age | Number of cysts | Size of main cyst (cm) | Mitoses/HPF 400× | Cell atypia | Fibrosis score | Ki67 | Approximate development time (months) | Clinical diagnosis |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | F | 8 | 1 | 0.3×0.3 | 0 | − | 2 | 9, 66 | nd | Palpebral nodule |
| 2 | M | 8 | 2 | 0.5×0.5 | 0 | − | 2 | 19, 03 | 2 | Cyst |
| 3 | M | 8.5 | 2 | 0.5×0.5 | 0 | − | 2 | nd | 36 | Cyst |
| 4 | F | 12 | 1 | 0.9×0.7 | 0–2 | + | 1 | 19, 06 | 2 | Palpebral nodule |
| 5 | M | 12 | Multiple | Small ∗ | 0 | − | 3 | 16, 67 | nd | Palpebral nodule |
| 6 | M | 13 | Multiple | 0.4×0.3 | 0 | − | 1 | nd | 24 | Multiple palpebral nodules |
| 7 | M | 3 | 1 | 0.6×0.3 | 0 | − | 2 | 5, 30 | nd | Palpebral nodule |
| 8 | M | 7 | Multiple | Small ∗ | Occasional | − | 2 | 12, 62 | 12 | Pigmented nodule |
| 9 | M | 15 | Multiple | Small ∗ | 0 | − | 2 | 20, 83 | nd | Pigmented nodules |
Fibrosis score: 0=absent; 1=mild, 2=moderate; 3=severe; nd=not determined.
Multiple, variably sized cysts ranging in diameter form 55 to 200 μm.
Seven cases of hidrocystomas were referred, in clinical records, as variably sized dark coloured palpebral nodules (Fig 1); 2/9 cases were described as tense, dark reddish, cysts (Fig 2). The most common differential diagnosis posed by clinicians was eyelid melanoma. All cats were free from cutaneous lesions, other than on the eyelid skin.
Fig 1.
Male, Persian cat, 8.5 years old. A single, large, tense, smooth, dark brownish cyst is visible on the medial canthus at the eyelid margin. The lesion has been present for 3 years, with minimal size variations.
Fig 2.
Male, Persian cat, 15 years old. Multiple, small, smooth, pigmented nodules are present on upper eyelid margins.
Grossly, on cut section, 5/9 samples revealed a cystic lesion that leaked a small amount of reddish to brownish fluid; in 4/9 samples eyelid dermis was focally expanded with a spongy appearance.
Histologically, in 3/9 cases eyelid superficial dermis was expanded by a single large unilocular or multilocular well delimited, unencapsulated cyst (0.3–0.9 cm) (Fig 3); in 2/9 cases multiple small cysts were present beside a single large (0.5×0.5 cm) cystic formation. In 4/9 cases multiple, variable sized, small (55–200 μm) cysts were detectable. In all cases, the cystic wall was lined by cuboidal to flattened epithelial cells arranged in a single layer and only occasionally rising in short papillary projections sustained by a thin fibrovascular branching core. Multifocal epithelial erosions were also present.
Fig 3.
A single cyst expands the superficial eyelid dermis. Conglomerates of ceroid-loaded macrophages, admixed with fewer lymphocytes, are present within cystic lumen. Haematoxylin and eosin, 12.5×.
Epithelial cells were characterised by poorly defined cell borders, moderate to abundant finely vacuolated eosinophilic cytoplasm, occasionally with apical bulbous expansion (decapitation secretion), and voluminous oval, basally located, nuclei with a single prominent nucleolus.
No cell atypia was observed, except for case 4 where moderate anisokaryosis and anisocytosis were present. Mitoses were usually not detected, except for cases 4 and 8 (0–2 mitoses×HPF) (Fig 4).
Fig 4.
Epithelial cells lining cystic wall form short papillary projection protruding within lumen. Cells are characterised by moderate amount of eosinophilic, finely vacuolated cytoplasm and large vesicular nuclei, with single prominent nucleolus. A mitotic figure is present (arrow). Haematoxylin and eosin, 400×.
The epithelium of the cyst laid on a single row of spindle cells with minimal amount of lightly eosinophilic cytoplasm and small, oval, dense nuclei (myoepithelial cells). The cystic lumen was filled with a variable amount of amorphous homogeneous eosinophilic proteinaceous material, containing scattered red blood cells, foamy macrophages loaded with intracytoplasmic yellowish granular pigment (ceroid), non-degenerated neutrophils and, occasionally, large needle shaped crystals (cholesterol).
A mild, diffuse inflammatory cell infiltration, mostly composed by lymphocytes, plasma cells, macrophages, a lesser numbers of neutrophils and a few scattered mast cells, was present in surrounding dermis. In two cases (5 and 8) a small dermal aggregate of foamy macrophages and fewer multinucleated giant cells containing abundant intracytoplasmic ceroid pigment admixed with small cholesterol crystals (lipophagic granuloma) was present.
Dermal fibrosis was scored as mild in 2/9 cases, moderate in 6/9 cases (Fig 5) and severe in one single case.
Fig 5.
Multiple, irregularly shaped, variably sized cysts are visible in eyelid dermis, surrounded by moderate dermal fibrosis (blue stained collagen). Mallory staining, 40×.
In one case (case 9) a small (0.4 cm) well-differentiated tubular adenocarcinoma of apocrine gland was also present in the eyelid dermis close to the cystic lesions.
In all cases, overlaying eyelid epidermis was diffusely, moderately hyperplastic, with focal mild spongiosis and orthokeratotic hyperkeratosis.
Immunohistochemically, in 7/8 cases tested a diffuse and intense intracytoplasmic staining with cytokeratin 8/18 and 19 was observed in epithelial cells lining cystic wall. A small rim of flattened, α SMA and CK14 positive cells surrounded cyst epithelium (myoepithelial cells) in 7/8 cases. Ki67/MIB1 nuclear staining was detected in 7/8 samples; PI ranged from 5.3 to 20.83 in different cases (mean 14.74; median 16.67; SD 5.73) (Fig 6). In normal Moll's glands included in the specimens, only few, scattered nuclei stained Ki67/MIB1 positive (mean PI 1.9).
Fig 6.
Multiple, scattered nuclei are intensely and diffusely immunolabelled with MIB1 antibody. MIB1/Ki67 immunostaining, chromogen AEC (intense red-brown staining), 200×.
One case (case 6) was poorly reactive to immunohistochemical staining, probably due to prolonged formalin fixation.
At the time of this paper, none of the hidrocystomas had recurred.
Discussion
Hidrocystoma are benign cystic lesions of sweat apocrine glands that, in man, can originate both from eccrine and apocrine glands. Apocrine hidrocystoma usually appear as a single cystic nodule on the face, occasionally on ears and scalp. 14–16
In the eyelids, hidrocystomas originate from apocrine sweat gland of Moll and usually present as multiple lesions on the lid margins. 14,17 Moll gland hidrocystomas have been described, in man, as sporadic findings or along with a constellation of other signs, ie, hypodontia, hypotrichosis, palmoplantar hyperkeratosis and onychodystrophy, as part of a rare autosomal recessive ectodermal dysplasia syndrome, the Schöpf–Schulz–Passarge syndrome. 18,19
In the feline species, a few cases of multiple eyelid apocrine cysts, resembling Moll apocrine hidrocystoma of human beings, have been described. 9–12 None of the cats in previous reports, as well as those examined in this series, had clinical signs consistent with ectodermal dysplasia (as described in man), and for all of them multiple eyelid cysts were the only complaint.
Most cases of feline eyelid hidrocystomas reported so far have been observed in Persian cats, suggesting a breed predisposition. 9–12 Our data seem to confirm this hypothesis, as all cats in our caseload were of Persian breed.
No sex predisposition has been reported for eyelid hidrocystomas in humans or cats, and an equal number of female and male cats have been reported to be affected. In our series of cases male cats were overrepresented (seven males vs two females), however, this finding could reflect the distribution of the feline population and not related to an actual sex predisposition.
Consistently with previous reports in the feline species, 9,10 hidrocystomas in our caseload were mostly observed in older cats, with a median age of 8 years.
Clinical, gross and histological features of our cases were consistent with previous reports of human and feline hidrocystomas. The dark colour of the lesions could be ascribed to the presence of blood, haemosiderin and ceroid pigments within cyst lumen. These findings in turn being related to focal epithelial ulceration and secondary haemorrhages.
The immunophenotype of epithelial cells lining cystic lesions (CK8/18 and CK19 positive) and of underlying myoepithelial cells (α SMA and CK14 positive) was most consistent with apocrine gland features. 20
The aetiopathogenesis of hidrocystoma, both in human and feline species, is debated and hidrocystomas have been variably interpreted as apocrine gland retention cysts or as benign neoplasms. 4,8,10,15 Epithelium flattening and dermal fibrosis around cystic structures apparently support the hypothesis of a retention cyst. 8 On the other hand, high proliferative indices and epithelial papillary projections have been considered features of neoplastic transformation. 5,10
Based on our data, no definite conclusion concerning hidrocystoma aetiopathogenesis was possible, although, according to previous authors, 10 the PI (Ki67 immunostaining) observed, relatively high when compared with normal Moll's gland epithelium, suggested a proliferative nature of these cystic lesions.
The presence of the relevant amount of dermal fibrosis in all samples tested could be interpreted as playing a role in cyst formation, but also as a lesion secondary to compression exerted by hidrocystoma on surrounding dermis.
Further studies on a larger number of specimens are needed to confirm the proliferative nature of this rare condition.
Acknowledgements
The authors are grateful to all those colleagues that provided cases for this study, specifically: Dr Adolfo Guandalini, Dr Damiano Stefanello, Dr Re Calegari, Dr Anna Refatti and Dr Fumagalli.
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